The graphite has such unique properties associated with its layer structure as anisotropies in thermal and electrical conductivity. However, the synthesis of graphite is required extreme conditions of pressure and temperature due to the fact that it has inaccessible melting point and the extremely low sublimation pressure. For example, so called HOPG (Higly Oriented Pyrolitic Graphite) is prepared by decomposing a gaseous hydrocarbon (e.g. methane) at 2,000.degree. C. and then hot pressing the resulting pyrolytic carbon at still higher temperature. It is now well known that most carbonaceous materials are well graphitized when they are subjected to a heat treatment at higher temperature above 2,500.degree. C. On the other hand, there have been many efforts to prepare pyrolytic carbons, at the low decomposition temperature utilizing dehydrogenation, dehydrohalogenation, decarbonic acid, dehydration of selected hydrocarbons. However, the carbon deposits thus obtained are of so poorly ordered state that they are insufficient to provide anisotropic materials or device made therefrom. There also has been known carbon fiber which is obtained by the heat treatment of fibrous polymer compound at high temperature. These carbon fibers are widely used for structural materials, but their instability in physical properties debases their usefulness for new electronic materials or devices utilizing anisotropic electrical and thermal conductivity. They also lack reproducibility.
To modify graphite leads to establishment of a variety degrees of anisotropy, there have been studied many kinds of graphite intercalation compounds (GIC) which are achieved by allowing metal atoms, metal halides or acids to be inserted between adjacent graphite layers of a host graphite material.
Hitherto, many studies have been made on methods for inserting the materials to be inserted between the adjacent graphite layers. For example, a vapor-reaction method (two-bulb method), a solvent method, an electrochemical method, a mixing method, a pressure method and the like are suggested in "Carbon", published by Carbon Material Society, vol. 111, page 171 (1982). A large number of the material to be inserted are already known (Advances in Physics, 30, 139(1981), for example alkaline metals (e.g. Li, Na, K, Rb, Cs, etc.), alkaline earth metals (e.g. Ca, Sr, Ba, etc.), rare earth metals (e.g. Sm, Eu, Yb, etc.), halogen molecules, e.g. Br.sub.2, I.sub.2, ICl, Cl.sub.2, etc.), halides (for example fluorides, e.g. KrF.sub.2, BF.sub.3, PF.sub.3, AlF.sub.3, BrF.sub.3, SiF.sub.4, TiF.sub.4, XeF.sub.4, PF.sub.5, AsF.sub.5, SbF.sub.5, NbF.sub.5, TaF.sub.5, IF.sub.5, MoF.sub.6, WF.sub.6, UF.sub.6, etc.; chlorides, e.g. MgCl.sub.2, ZnCl.sub.2, CdCl.sub.2, HgCl.sub.2, MnCl.sub.2 , FeCl.sub.2, CoCl.sub.2, NiCl.sub.2, PdCl.sub.2, CuCl.sub.2, BCl.sub.3, AlCl.sub.3, GaCl.sub.3, InCl.sub.3, TlCl.sub.3, CrCl.sub.3, FeCl.sub.3, RuCl.sub.3, OsCl.sub.3, AuCl.sub.3, YCl.sub.3, SmCl.sub.3, EuCl.sub.3, GdCl.sub.3, TbCl.sub.3, DyCl.sub.3, HoCl.sub.3, ErCl.sub.3, TmCl.sub.3, YbCl.sub.3, LuCl.sub.3, ZrCl.sub.4, HfCl.sub.4, SbCl.sub.4, BiCl.sub.5, NbCl.sub.5, TCl.sub.5, MoCl.sub.5, UCl.sub.5, TeCl.sub.6, WCl.sub.6, etc.; bromides, e.g. CrBr.sub.2, HgBr.sub.2, FeBr.sub.2, AlBr.sub.3, GaBr.sub.3, TlBr.sub.3, FeBr.sub.3, AuBr.sub.3, UBr.sub.5 etc.), oxides (e.g. H.sub.2 O.sub.5, SO.sub.3, SeO.sub.3, CrO.sub.3, MoO.sub.3, Cl.sub.2 O.sub.7, Be.sub.2 O.sub.7, etc.), acids (e.g. HNO.sub.3, H.sub.2 SO.sub.4, HClO.sub.4, HF, CF.sub.3 COOH etc.) and intermetallic compounds (e.g. alkaline metal-mercury, mercury-bismuth, etc.) and the like.
However the common method such as two-zone vapor transport technique and electrochemical reaction method as well as other several novel methods, essentially achieved by direct contact of liquid or gaseous species with host graphite, was applied to such limited reagents that have low melting point or high vapor pressure. Most of these compounds with graphite elaborated by these methods are not only unstable but are also sensitive to heat. There have not been reported an air stable GIC in which intercalant is fixed firmly, nor a practical utilization of the anisotropic properties involved the new electronic device.
Inpurity doping is another method of controlling the degree of anisotropy or the type of conductivity (P-type or N-type). But the fact that graphite is themodynamically very stable refuses the diffusion technique often used in the fabrication of doped silicon or germanium semiconductor. Accordingly, doped graphite has not been reported.